There is known the "Cutfast" high-speed method of thermomechanical machining developed by the PERA Company of Great Britain. In this method the surface being removed is preheated by a plasma arc with the anode spot located in advance of the cutting tool.
This method resides in localized preheating of the surface to be cut by a plasma arc and substantially simultaneous chip removal. Heat resistant tools are employed, since cutting is effected in the heat-affected zone.
However, the process is costly and its application is inherently limited because of the employment of pure argon as a plasma-forming gas.
Machining efficiency in this method is improved by increasing the cutting speed at invariable or even reduced tool feed compared with machining without heating. In turn, this increase in the cutting speed makes it impossible to machine heavy unbalanced workpieces having an eccentricity, since such an increase in the cutting speed leads to greater impact loads and results in premature wear and failure of the tool. Also, increased workpiece rotation speed and the accompanying impact loads entail faster wear of the equipment.
The above method fails to provide for machining many active metals, such as titanium and its alloys, because the thin chip heated to a very high temperature becomes self-inflammable as a result of the exothermic reaction when the chip is oxidized by the air. Further, in the "Cutfast" process tool life is reduced because it is in continuous contact with the alpha-layer in the zone of the anode spot.
In view of the foregoing, this known method is intended for machining by a single-edged cutting tool with small depth and width of cut.